1. Field of the Invention
This invention relates generally to methods of and apparatus for controlling gas pressure, and, more particularly, to methods of and apparatus for controlling a gas flame at a torch tip by controlling the pressure at the tip.
2. Description of the Prior Art
In many manufacturing operations a small flame at a torch tip is used for a variety of different purposes, such as cutting. The gas for the torch is often fueled by a gas generated by disassociation of an electrolytic solution. One example of this type of torch is manufactured by Henes Manufacturing Co. under the registered trademark "Water Welder." This device uses water as the electrolytic solution and generates hydrogen and oxygen gases by disassociation of the water when an electrical current is supplied to the generator. The application of the current is controlled by a triac circuit.
In manufacturing semiconductor devices gas torches are frequently used. For example, in the manufacture of devices such as diodes, transistors, and light-emitting diodes, a gas torch is used to form a ball at the severed end of a wire. This ball is then bonded to a portion of the device.
In the past maintenance of a uniform flame for these gas torches has been a problem. Frequently, the operations in question require changing the torch tips with some regularlity, and this can greatly affect the gas pressure at the torch tip. Since these pressure changes can result in an unsatisfactory flame, an operator must completely readjust the voltage control circuit to again obtain a proper flame. Also, impurities in the electrolyic often make it difficult to maintain a uniform flame. Changes in the electrolyte level and temperature can also cause variations in the rate of disassociation and thereby affect the flame uniformity.
Past attempts at maintaining a uniform flame have been limited to providing an operator to manually adjust the firing of a triac firing circuit. This has proven both time consuming and wasteful since much of the product is often ruined during the adjustment period.